The details of the US's apparent ejection from its only remaining base in ex-Soviet Central Asia remain murky, but initial reports suggest that the US was simply outbid by Russia. Russia offered a $2bn aid package to Kyrgyzstan, and the US's $150m annual payments to Kyrgyzstan suddenly looked pretty paltry. Underscoring the point, the president of Kyrgyzstan made the announcement not at home, but while on a trip to Moscow.

So it's tempting to write this off as bazaar politics. But the seeds for this move were sown last August in Georgia, when the US failed to do anything substantial to support its close ally in its war against Russia. Georgia, remember, sent a quarter of its armed forces to Iraq, despite the presence of two festering conflicts on its own soil, solely to curry favour with the US. It enacted free-market economic reforms so quickly, and in spite of significant social dislocation, that it was named the top reforming country in the world by the World Bank.

So when Georgia went to war with Russia and the US stood by, it sent a strong signal to the rest of America's would-be allies in the former Soviet Union. (Remember also, while it's now clear that Georgia and Russia were both culpable for that war breaking out, as soon as fighting started US officials immediately blamed Russia.) If the US isn't going to defend Georgia, would it defend Azerbaijan, or Ukraine or Kazakhstan?

Kyrgyzstan has apparently answered that question for itself by jettisoning the Americans in favour of Russia. The US base has been controversial in Kyrgyzstan. There were disputes over fuel dumping, the shooting of a Kyrgyzstan citizen by an American base guard and the rent paid by the Americans. In 2007, Kyrgyzstan raised the rent from $2m a year to about $63m a year, and the US provides a total aid package to the country of about $150m a year. While Kyrgyzstan officials frequently complained about the base, US officials believed it was just a bargaining technique, intended to drive up the price. (Russia has its own airbase in Kyrgyzstan, for which it pays no rent.)

I was in Kyrgyzstan about 18 months ago, and one diplomat told me: "I don't think Kyrgyzstan is interested in driving out the base. … The US is providing about $150m a year in aid, and they have to expect that if the airbase leaves some of that will disappear, and Russia and China won't be able to compensate for it." Well, Russia has called America's bluff, again.

The base is a supply hub for US operations in Afghanistan, and the implications of its closure on the US effort there would likely be dire. The US has already been kicked out of one base in Central Asia, the Karshi-Khanabad air base in Uzbekistan. And the US – about to double its footprint in Afghanistan – was already struggling to figure out how to get the extra supplies there, even before Kyrgyzstan's announcement.

Which makes the apparent Russian hand behind this move all the more puzzling. Conventional wisdom about the base said that Russia, while occasionally complaining about it in public, privately wanted it to stay. Russia was just as afraid of Islamist extremism as was the US, this logic went, and was perfectly happy to have the US spending its blood and treasure defeating the Taliban.

According to Russia's Nato representative, that logic has now been reversed, arguing that the US presence in Afghanistan is actually fomenting instability there: "Americans' failure in Afghanistan is creating a bigger threat to neighbouring countries. Military actions, which are being aimed against civilians, helped those who were not going to take sides with the Taliban movement and other extremists," he said, by way of explaining the Kyrgyzstan government's decision.

It's not clear whether we should take this statement at face value. Were Churchill alive for Putin's Russia, he surely would have added a couple extra layers of inscrutability to the "riddle, wrapped in a mystery, inside an enigma" line. The second part of Churchill's quote, though, is less often remembered: "But perhaps there is a key. That key is Russian national interest." Russia has apparently decided that thwarting the US military presence in Central Asia is now more in its interest than supporting the US in Afghanistan.

But Kyrgyzstan should be able to stand up to Russian threats or bribery, as long as it has a little backup. What the US showed in Georgia, though, is that in the end Kyrgyzstan is on its own.